1. Field of the Invention
The present invention relates to an after-burner system and more particularly to an after-burner system for an exhaust emission control system of an engine to reduce Hydrocarbon in exhaust gas.
2. Description of the Related Art
In recent years, a severe emission control has been needed for an engine to protect the Earth environment from pollution. Particularly, it is necessary to reduce Hydrocarbon. Hydrocarbon is contained in unburned mixture which is generated by an imperfect burning in the engine. A catalyzer to purify Hydrocarbon is located in an exhaust pipe of the engine. Much Hydrocarbon is released from the exhaust pipe to the atmosphere when the engine temperature is cold, since the catalyzer does not act sufficiently when the catalyzer temperature is cold. That is, the catalyzer acts sufficiently when the catalyzer temperature is in a certain high temperature region (ex. over 200 degrees Celsius).
For example, to increase the catalyzer temperature, the catalyzer is heated by an after-burner system. A conventional after-burner system 800 for an engine 801 shown in FIG. 10, is disclosed in Japanese Patent Laid-open No. 63(1988)-68714. Here, the engine 801 has an intake passage 802 and an exhaust passage 803. A catalyzer 804 is inserted into the exhaust passage 803. Both ends 805, 806 of a bypass passage 807 are connected with the exhaust passage 803 at an upper stream side of the catalyzer 804. A switching valve 808 is located at a connecting point between the exhaust passage 803 and the end 805. The switching valve 808 is controlled by a control unit 809 which has input thereto a signal from a temperature sensor 810. An adsorbent 811 is inserted into the bypass passage 807. A fuel reforming device 812 is inserted into the exhaust passage 803 at an upper stream side of the switching valve 808. The fuel reforming device 812 has an input passage 813 and an output passage 814. One end of the output passage 814 opens into the exhaust passage 803 at an upper stream side of the catalyzer 804. A filter 815 is inserted into the output passage 814. A passage 816 connects the filter 815 with the intake passage 802.
In the after-burner system 800, when the engine 801 is cold, the catalyzer 804 is also cold. At this time, the fuel reforming device 812 reforms fuel (ex. methyl alcohol) into Hydrogen and other components. Hydrogen separated at the filter 815 is only supplied to the catalyzer 804 via the output passage 814. At the catalyzer 804, Hydrogen is burned and the catalyzer 804 is heated. Here, an igniting device (not shown) requires a strong igniting power for rapid heating of the catalyzer.